1. Field of the Invention
The present invention relates to a coating method and apparatus for a heat-development photo-sensitive material.
2. Description of the Related Art
In the field of medical diagnosis film and photomechanical film, liquid wastes should be reduced from the point of view of environmental protection and space saving. A heat-development photo-sensitive material can be efficiently exposed by a laser image setter or a laser imager, and a high-resolution black image can be formed on it. The heat-development photo-sensitive material does not need solution processing pharmaceuticals to realize a simple environment-protecting heat-development processing system.
The heat-development photo-sensitive material is produced in such a manner that a photo-sensitive layer and a protective layer are formed on a web. The photo-sensitive layer includes organic silver oxide, photo-sensitive silver halide, and hydrophobic polymer latex or the like as a binder, and the protective layer includes at least one water-soluble polymer as a binder. Since viscosity characteristics of the two layers are remarkably different, the layers easily become uneven in thickness and have streaks.
Since the heat-development photo-sensitive material is a new material, a technology for efficiently forming the layers on the continuously-running web and a technology for preventing thickness unevenness of the layers and streaks on the layers have not been established.
In addition, since coating liquids for the layers include organic solvents, the organic solvents in the layers on the web volatilize at the heat developing stage which pollutes the environment. The organic solvents also volatilize at the production of the heat-development photo-sensitive material.
In view of the foregoing, it is an object of the present invention to provide a coating method and apparatus for efficiently forming a photo-sensitive layer and a protective layer and producing a high-quality heat-development photo-sensitive material without thickness unevenness and streaks. It is also an object of the present invention to provide a coating method and apparatus that does not pollute the environment.
To achieve the above-mentioned object, the present invention is directed to a coating method for a heat-development photo-sensitive material produced in such a manner that at least one photo-sensitive layer including at least one organic silver oxide and at least one hydrophobic polymer latex as binders and at least one protective layer including at least one water-soluble polymer as binders are formed on a web, wherein: coating liquids for the photo-sensitive layer and the protective layer are supplied to manifolds of a slide bead hopper, and pushed out onto a slide surface through supply slots connected to the manifolds to form layers while flowing down the slide surface, and the web that is wound on a back-up roller and continuously running is coated with the layers; and each coating liquid is supplied from a first end of each manifold to a second end of the manifold, and pressure loss of each coating liquid flowing through each supply slot becomes smaller from the first end to the second end to cancel pressure loss of the coating liquid flowing through the manifold.
To achieve the above-mentioned object, the present invention is directed to a coating apparatus for a heat-development photo-sensitive material produced in such a manner that at least one photo-sensitive layer including at least one organic silver oxide and at least one hydrophobic polymer latex as binders and at least one protective layer including at least one water-soluble polymer as binders are formed on a web, wherein: coating liquids for the photo-sensitive layer and the protective layer are supplied to manifolds of a slide bead hopper, and pushed out onto a slide surface through supply slots connected to the manifolds to form layers while flowing down the slide surface, and the web that is wound on a back-up roller and continuously running is coated with the layers; and each coating liquid is supplied from a first end of each manifold to a second end of the manifold, and each supply slot becomes shorter from the first end to the second end.
Since the coating liquid for the photo-sensitive layer does not gel and is thixotropic, it is important how to make the liquid amount uniform along the width of a supply slot (coating width) from which the liquid flows in order to prevent the thickness unevenness and the streaks.
According to the present invention, each coating liquid is supplied from a first end of each manifold to a second end of the manifold, and pressure loss of each coating liquid flowing through each supply slot becomes smaller from the first end to the second end to cancel pressure loss of the coating liquid flowing through the manifold. Each supply slot becomes shorter from the first end to the second end. This makes the liquid amount uniform along the width of the supply slot, and thus the layers can be well formed without defects. There may be one photo-sensitive layer and one protective layer, and there may be two or more photo-sensitive layers and two or more protective layers. There may be an intermediate layer between the photo-sensitive layer and the protective layer.
Moreover, the layers can be well formed even if the solvents of the layers are mainly water. Thus, the organic solvents are not needed, and this does not pollute the environment. The solvent is water means that the concentration of the water in the solvent is 30 percent or higher, preferably 50 percent or higher, more preferably 70 percent or higher, by weight. The other component of the solvent is a water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide and ethyl acetate.